Tetrazoles: Unique Capping Ligands and Precursors for Nanostructured Materials

Capping agents play an important role in the colloidal synthesis of nanomaterials because they control the nucleation and growth of particles, as well as their chemical and colloidal stability. During recent years tetrazole derivatives have proven to be advanced capping ligands for the stabilization of semiconductor and metal nanoparticles. Tetrazole‐capped nanoparticles can be prepared by solution‐phase or solventless single precursor approaches using metal derivatives of tetrazoles. The solventless thermolysis of metal tetrazolates can produce both individual semiconductor nanocrystals and nanostructured metal monolithic foams displaying low densities and high surface areas. Alternatively, highly porous nanoparticle 3D assemblies are achieved through the controllable aggregation of tetrazole‐capped particles in solutions. This approach allows for the preparation of non‐ordered hybrid structures consisting of different building blocks, such as mixed semiconductor and metal nanoparticle‐based (aero)gels with tunable compositions. Another unique property of tetrazoles is their complete thermal decomposition, forming only gaseous products, which is employed in the fabrication of organic‐free semiconductor films from tetrazole‐capped nanoparticles. After deposition and subsequent thermal treatment these films exhibit significantly improved electrical transport. The synthetic availability and advances in the functionalization of tetrazoles necessitate further design and study of tetrazole‐capped nanoparticles for various applications.     

Protein-templated semiconductor nanoparticle chains

Cadmium sulfide and lead sulfide semiconducting nanoparticle chains have been fabricated for the first time by exploiting a general property of proteins, amyloidogenicity. The diameter of the CdS and PbS nanowires was tuned in the range of ～50 to ～350?nm by changing the process parameters. The nanoparticle chains were characterized by field emission scanning electron microscopy, UV-visible spectroscopy, transmission electron microscopy, electron energy loss spectroscopy and high-resolution transmission electron microscopy.     

On the solution self-assembly of nanocolloidal brushes: insights from simulations

The synthesis of novel nanoparticles with exceptional properties continues to stimulate the search for advanced applications in fields as diverse as solar energy harvesting and polymer reinforcement. It is widely recognized that to practically exploit the promised benefits it is necessary to guide the assembly of the various nanoparticles into well-defined supra-molecular structures. Towards this goal, we report Monte Carlo simulation results for the self-assembly of spherical nanoparticles in implicit solvent. The nanoparticles interact solely via dispersive interactions, modeled as square-well potentials. To control the morphology of the self-assembled aggregates, side chains are grafted on specific locations on the nanoparticle surface (i.e., on the equator, on the tropics, on the entire tropical region, or uniformly on the nanoparticle surface). The results are discussed in terms of average cluster size, probability of observing aggregates of given size, and aggregate radius of gyration and asphericity as a function of the aggregate size. The parameters of interest are the solution conditions and the nanoparticle volume fraction (always in the dilute regime). As shown in previous reports (e.g., Striolo 2007 Small 3 628), the nanoparticles form insoluble agglomerates in the absence of the side chains. When the side chains are long and uniformly distributed on the nanoparticles, these remain individually dispersed in solution. More importantly, when the side chains are grafted on selected locations on the nanoparticles, these self-assemble, yielding structures composed of up to 7-10 nanoparticles. The number of grafted side chains is the parameter that predominantly determines the average aggregate size, while the aggregate morphology can be tuned by appropriately controlling the distribution and length of the grafted side chains.     

Ultrasonic-template method synthesis of CdS hollow nanoparticle chains

A facile and efficient ultrasonic-template method has been developed for the fabrication of CdS hollow nanoparticle chains. The structures and morphologies of products were characterized by XRD and TEM. UV-Vis and photoluminescence (PL) spectra recorded the optical properties of CdS hollow nanoparticle chains, which showed obvious blue shift relative to the CdS bulk materials. Systematic studies found that the ultrasonic irradiation, concentration of template (polyacrylicamide) and injection method of reaction solution in the system were important factors on the controlled synthesis of hollow nanoparticle chains. The possible mechanism for the formation of CdS hollow nanoparticle chains was also discussed.     

Sol–gel derived ZnO/PVP nanocomposite thin film for superoxide radical sensor

Pure ZnO films and ZnO nanoparticle-dispersed polyvinylpyrrolidone (PVP) composite films are prepared on Pyrex glass substrates by the sol–gel dip-coating technique utilizing zinc acetate precursor. The thin films are extensively characterized for surface morphology, chemistry, and nanocrystallite size using various advanced analytical techniques including Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). For the processing conditions considered, ZnO semiconductor thin films with nanocrystallite size 20–30 nm are obtained. The ZnO nanoparticle size in the PVP composite film increases with increase in ZnO content. The resistance of both the synthesized ZnO and ZnO/PVP thin films decrease significantly after exposure to solution containing superoxide anion radicals (SOR). The results thus indicate that ZnO and ZnO/PVP composite thin films can be used as biosensors for SOR and potentially for characterizing the antioxidant properties of fluids.     

Synergistic Effect of Hydroxyl and Carboxyl Groups on Promoting Nanoparticle Occlusion within Calcite

Direct occlusion of guest nanoparticles into host crystals enables the straightforward preparation for various of nanocomposite materials with emerging properties. Therefore, it is highly desirable to elucidate the ‘design rules’ that govern efficient nanoparticle occlusion. Herein, a series of sterically-stabilized nanoparticles are rationally prepared, where the surface stabilizer chains of such nanoparticles are composed of either poly(methacrylic acid), or poly(glycerol monomethacrylate), or poly((2-hydroxy-3-(methacryloyloxy)propyl)serine). Systematic investigation reveals that hydroxyl groups and carboxyl groups play a synergistic role in driving nanoparticle incorporation into calcite crystals, where the hydroxyl groups enhance colloidal stability of the nanoparticles and the carboxyl groups provide binding sites for efficient occlusion. The generality of these findings is further validated by extending it to polymer-stabilized gold nanoparticles. This study demonstrates that precision synthesis of polymer stabilizers comprising of synergistic functional groups can significantly promote nanoparticle occlusion, thus enabling the efficient construction of organic-inorganic hybrid materials via nanoparticle occlusion strategy.     

单分散金属硫化物纳米颗粒的简单制备方法

提出了一种制备单分散金属硫化物纳米颗粒的简单方法。在低热条件下疏水性三硫代碳酸盐分解释放出活性硫元素和硫醇,可分别作为反应体系的供硫剂和表面活性剂,产物金属硫化物纳米晶因吸附硫醇而保持良好的分散性。通过该法制备了A＆s和cu2s纳米颗粒,在对其形貌和尺寸表征的基础上,对其形成机制进行了讨论。     

Precisely Size‐Tunable Monodisperse Hairy Plasmonic Nanoparticles via Amphiphilic Star‐Like Block Copolymers

In situ precision synthesis of monodisperse hairy plasmonic nanoparticles with tailored dimensions and compositions by capitalizing on amphiphilic star‐like diblock copolymers as nanoreactors are reported. Such hairy plasmonic nanoparticles comprise uniform noble metal nanoparticles intimately and perpetually capped by hydrophobic polymer chains (i.e., “hairs”) with even length. Interestingly, amphiphilic star‐like diblock copolymer nanoreactors retain the spherical shape under reaction conditions, and the diameter of the resulting plasmonic nanoparticles and the thickness of polymer chains situated on the surface of the nanoparticle can be readily and precisely tailored. These hairy nanoparticles can be regarded as hard/soft core/shell nanoparticles. Notably, the polymer “hairs” are directly and permanently tethered to the noble metal nanoparticle surface, thereby preventing the aggregation of nanoparticles and rendering their dissolution in nonpolar solvents and the homogeneous distribution in polymer matrices with long‐term stability. This amphiphilic star‐like block copolymer nanoreactor‐based strategy is viable and robust and conceptually enables the design and synthesis of a rich variety of hairy functional nanoparticles with new horizons for fundamental research on self‐assembly and technological applications in plasmonics, catalysis, energy conversion and storage, bioimaging, and biosensors.     

Induced synthesis and characterisation of Ag and Ag2S assembly nanoparticle chains

A facile and efficient template method was developed for the fabrication of Ag and Ag₂S nanoparticle chains. The morphologies and structures of products were characterised by X-ray powder diffraction and transmission electron microscopy. The result shows that the length of Ag and Ag₂S nanoparticle chains are up to several micrometres. Systematic studies exhibit that the concentration of template (polyacrylamide) reagent, reaction solution and ageing time are important factors on the control synthesis of nanoparticle chains. The possible mechanism for the formation of Ag and Ag₂S nanoparticle chains was also discussed. The physical and chemical properties of the Ag and Ag₂S nanoparticle chains were investigated and their phytotoxicities were also researched for the first time. The phytotoxic result shows that the Ag and Ag₂S nanoparticle chains have obvious inhibition of seed germination.     

纳米SiO_2与有机物分子的亲和性和分散性

介绍纳米SiO2的合成和粒子表面的粗糙形貌以及纳米粒子链具有类似高分子链的弹性力学属性,研究纳米SiO2的亲合性,探讨亲合性对纳米SiO2的分散、改性、应用的影响。研究表明,在极性外加剂(如乙二胺、乙二醇、PEG、PDMS、PTHF、PMMA、PBMA等)存在的情况下,纳米SiO2的弹性粒子链和硅烷醇对SiO2的分散和改性具有显著的影响。带有大烷基侧链的高分子链与SiO2表面的亲合能较低,而带有官能团的高分子链与SiO2表面具有较高的亲合性。     

Effect of SH-containing ligands on the growth of CdS nanoparticles

Cadmium sulfide nanoparticles have been synthesized via precipitation from solution, using thioglycolic acid (TGA) and L-cysteine as stabilizing agents. The nanoparticle size has been evaluated using the absorption spectra of the solutions, dynamic light scattering data, and transmission electron microscopy. The L-cysteine-stabilized nanoparticles are smaller and more uniform in size compared to the TGA-stabilized nanoparticles. The effect of synthesis temperature on nanoparticle growth has been studied. With increasing synthesis temperature, the average radius of the nanoparticles increases, which is accompanied by their aggregation and broadening of their size distribution.     

Thermal and electrical behavior of silver chloride/polyaniline nanocomposite synthesized in aqueous medium using hydrogen peroxide

Nanocomposites of AgCl/PANI were synthesized by chemical polymerization/precipitation in aqueous HCl solution using both aniline monomer and AgNO₃ precursors in different molar ratio in PVP. Silver ions interact with PVP which restrict the bulk growth of AgCl and keep it in nanosized. During synthesis, AgCl NPs got entrapped in PANI chains through inter-chain hydrogen bonding. TGA studies showed complete decomposition of polymer chains occurred at 30–40 °C higher temperature than PANI alone. DSC studies indicate higher thermal stability of the composite, which is due to more heat flow for decomposition of polymer chains indicating compact packing of polymer matrix with AgCl NPs having large surface area to volume ratio. The TEM image showed spherical NPs were randomly dispersed in a polymer matrix and from XRD data crystalline nature of composite was seen. In FT-IR spectrum strong absorption band of a carbonyl stretching group due to PVP indicates its presence on nanoparticle surface in composite. Thin films of nanocomposite were spin casted on ITO coated glass surface. Electrical conductance was calculated from I–V data which was found to be in the range of 10^?2–10^?7 S cm^?1 depending on the concentration of NPs in it. These composites may find applications in solar cells as semiconductor material and for designing multiarray sensors for quality interpretation of beverages on the basis of their conductance changes using soft computing techniques.     

In Situ Passivation for Efficient PbS Quantum Dot Solar Cells by Precursor Engineering

Current efforts on lead sulfide quantum dot (PbS QD) solar cells are mostly paid to the device architecture engineering and postsynthetic surface modification, while very rare work regarding the optimization of PbS synthesis is reported. Here, PbS QDs are successfully synthesized using PbO and PbAc₂ · 3H₂O as the lead sources. QD solar cells based on PbAc‐PbS have demonstrated a high power conversion efficiency (PCE) of 10.82% (and independently certificated values of 10.62%), which is significantly higher than the PCE of 9.39% for PbO‐PbS QD based ones. For the first time, systematic investigations are carried out on the effect of lead precursor engineering on the device performance. It is revealed that acetate can act as an efficient capping ligands together with oleic acid, providing better surface coverage and replace some of the harmful hydroxyl (OH) ligands during the synthesis. Then the acetate on the surface can be exchanged by iodide and lead to desired passivation. This work demonstrates that the precursor engineering has great potential in performance improvement. It is also pointed out that the initial synthesis is an often neglected but critical stage and has abundant room for optimization to further improve the quality of the resultant QDs, leading to breakthrough efficiency.     

Synthesis of silver nanoparticles from carboxylate precursors under hydrogen pressure

A direct, high yield synthesis for preparing narrow-size silver nanoparticles by decomposition of silver carboxylate precursor under H₂ pressure (3 bars) in solution is reported. The method corresponds to that for nanoparticles synthesised by thermal decomposition of carboxylic acid silver salts, but is faster, reproducible, versatile, and easier to control. Most of carboxylate groups are reprotonated upon the presence of dihydrogen and subsequent reduction of Ag⁺ produces spherical particles of dimensions 4–6 nm. The IR studies indicate that aliphatic carboxylates chemisorb on the nanoparticle surface with the two oxygen atoms coordinated mostly symmetrically and forming bridging bidentate Ag–O bonds. This implies strong interactions between the surfactant and Ag nanoparticle and enhances the stability of Ag colloid. There are some sites yet, probably at vertex or facet atoms of the nanoparticle, which form linkages of chelating bidentate or ionic character. Silver particles can be additionally capped in situ either by aliphatic primary amines or thiols forming mixed carboxylate/amine or carboxylate/thiol protecting monolayer. It is demonstrated that coordination of the second ligand adjusts physicochemical properties of nanoparticles. In the dual passivating system both amine and thiol were found to be tightly bounded to the silver nanoparticle surface.     

Biotemplated synthesis of metallic nanoparticle chains on an alpha-synuclein fiber scaffold

Biomolecular templates provide an excellent potential tool for bottom-up device fabrication. Self-assembling alpha-synuclein protein fibrils, the formation of which has been linked to Parkinson's disease, have yet to be explored for potential device fabrication. In this paper, alpha-synuclein fibrils were used as a template for palladium (Pd), gold (Au) and copper (Cu) nanoparticle chains synthesis. Deposition over a range of conditions resulted in metal-coated fibers with reproducible average diameters between 50 and 200 nm. Active elemental palladium deposited on the protein fibrils is used as a catalyst for the electroless deposition of Au and Cu. Nanoparticle chains were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectrometry (XEDS), and electron energy loss spectrometry (EELS).     

Facile microwave-combustion synthesis of wurtzite CdS nanoparticles

In this study we first report microwave-combustion synthesis of faceted CdS nanoparticles by using cadmium thiocyanate complex as a single source precursor. This is the first example of a metal-thiocyanate (M-SCN) complex being used as a source for metal sulfides (M-S) preparation in a microwave-combustion process. The synthesized CdS was characterized using X-ray diffraction (XRD), field mission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). The by-product assisted combustion synthesis yields CdS nanoparticles with the mixtures of octahedral geometries, hexagonal, and triangle plate morphologies and the sizes were found to be 100 nm to 5 microm. The XRD patterns imply the formation of well crystallized wurtzite CdS. The influence of cadmium and sulfur precursors and microwave irradiation time on the morphology of CdS nanoparticle was also investigated. The cadmium and sulfur precursors strongly influenced the CdS morphology and increasing the microwave irradiation time and intensity has no effect on the CdS morphology. In addition, a plausible mechanism of CdS nanoparticle formation has been proposed in this research.     

Structural characterization of CdS nanoparticles grown in polystyrene matrix by thermolytic synthesis

Cadmium sulfide nanoparticles embedded in a polystyrene matrix (CdS/PS) were successfully prepared by in situ thermolysis of a cadmium thiolate precursor dispersed in the polymer. The heat-induced formation of cadmium sulfide was studied by thermogravimetric analysis and differential thermal analysis, while the chemistry of the reaction forming the CdS/PS compound was investigated by nuclear magnetic resonance and X-ray photoelectron spectroscopy. The structural characterization was performed by X-ray diffraction and transmission electron microscopy. The CdS nanocrystals are single crystals of cubic phase (zincblende structure) of spherical shape. The average diameter of the nanocrystals embedded in the polystyrene matrix achieved by our synthesis process is as small as 2.5 ± 0.5 nm. Room temperature UV–VIS absorption spectra exhibit a shoulder at 412 nm that is consistent with the presence of CdS nanocrystals of ∅ ≈ 2 nm. The role of the polymer on the nanoparticle growth was also discussed.     

Efficient synthesis of PbTe nanoparticle networks

The synthesis of semiconductor nanocrystalline networks using weak capping ligands in aqueous media has been demonstrated. Carbohydrates, including ?-cyclodextrin, D-(+)-glucose, D-glucosamine, lactobionic acid, sucrose, and starch were chosen as weak ligands to facilitate the formation of PbTe nanoparticle networks. The nanoparticle size, ranging from 5 nm to 30 nm, can be tuned by manipulating the temperature and concentration. Through a similar strategy, more complicated nanostructures including carbohydrate spheres@PbTe core-shell structures and Te@carbohydrate@PbTe multilayered submicron cables have been fabricated. This is a general approach which can be easily extended to the fabrication of other semiconductor networks, including PbSe and Bi₂Te₃ using carbohydrates and ethylenediaminetetraacetic acid (EDTA), respectively, as ligands.     

Self-Assembly of Magnetic Nanochains in an Intrinsic Magnetic Dipole Force-Dominated Regime

Magnetic nanoparticle chains offer the anisotropic magnetic properties that are often desirable for micro- and nanoscale systems; however, to date, large-scale fabrication of these nanochains is limited by the need for an external magnetic field during the synthesis. In this work, the unique self-assembly of nanoparticles into chains as a result of their intrinsic dipolar interactions only is examined. In particular, it is shown that in a high concentration reaction regime, the dipole–dipole coupling between two neighboring magnetic iron cobalt (FeCo) nanocubes, was significantly strengthened due to small separation between particles and their high magnetic moments. This dipole–dipole interaction enables the independent alignment and synthesis of magnetic FeCo nanochains without the assistance of any templates, surfactants, or even external magnetic field. Furthermore, the precursor concentration ([M] = 0.016, 0.021, 0.032, 0.048, 0.064, and 0.096 m ) that dictates the degree of dipole interaction is examined—a property dependent on particle size and inter-particle distance. By varying the spinner speed, it is demonstrated that the balance between magnetic dipole coupling and fluid dynamics can be used to understand the self-assembly process and control the final structural topology from that of dimers to linear chains (with aspect ratio >10:1) and even to branched networks. Simulations unveil the magnetic and fluid force landscapes that determine the individual nanoparticle interactions and provide a general insight into predicting the resulting nanochain morphology. This work uncovers the enormous potential of an intrinsic magnetic dipole-induced assembly, which is expected to open new doors for efficient fabrication of 1D magnetic materials, and the potential for more complex assemblies with further studies.     

Positionally defined, binary semiconductor nanoparticles synthesized by scanning probe block copolymer lithography

We report the first method for synthesizing binary semiconductor materials by scanning probe block copolymer lithography (SPBCL) in desired locations on a surface. In this work, we utilize SPBCL to create polymer features containing a desired amount of Cd(2+), which is defined by the feature volume. When they are subsequently reacted in H(2)S in the vapor phase, a single CdS nanoparticle is formed in each block copolymer (BCP) feature. The CdS nanoparticles were shown to be both crystalline and luminescent. Importantly, the CdS nanoparticle sizes can be tuned since their diameters depend on the volume of the originally deposited BCP feature.